I'm having trouble finding my baby heartbeat

Mayra • Third time mommy to a beautiful baby girl Rosalia , Thalia , & Viviana we are adding our last baby and this time is a BOY 💙 in May 30, 2023.
I been having trouble finding my baby heartbeat with the home Doppler . I'm 13weeks and 4 days . Have any of you girls had trouble finding heartbeat? I'm worry ! I have my ultrasound appointment next Monday . I'm so nervous.